Project Summary/ Abstract Coordination of growth and morphogenesis during development is critical for formation of organs of proper shape and size and improperly sized and shaped organs often lead to organ malfunction and congenital anomalies. The protocadherins, Dachsous (Ds) and Fat constitute a highly conserved signaling pathway that regulates growth through its influence on Hippo signaling and morphogenesis by regulating planar cell polarity and oriented cell divisions. Consistently, mutations affecting this pathway result in a number of diseases affecting organ shape or size. Studies in Drosophila have provided important insights into the molecular mechanisms that regulate organ size and shape by Fat signaling. Recently I have identified a new gene Vamana, which is a critical downstream component of the Fat signaling pathway. Additionally, my recent work has identified several novel regulators of this pathway and has led to intriguing findings that suggest that vesicular trafficking plays a crucial role in regulating Fat signaling, an aspect that is very little explored. In Aim 1, I propose to investigate the vesicular trafficking mechanisms that organize this signaling pathway. Specifically, I will study the interplay of ubiquitination and palmitoylation in trafficking of the components of this pathway. From a pilot genetic screen, I have recently isolated a novel mutation, Big round wings (Brw), which displays phenotypes characteristic of mutations in Fat-signaling pathway. In Aim 2, I will characterize how Brw, regulates this pathway. Finally, based on the success of the pilot screen, I propose to identify additional regulators of Fat signaling by an innovative forward gain of function screen. While my recent work has enabled me to generate these intriguing findings and the research plan, my immediate goals are to obtain additional training in live imaging, vesicular trafficking, ubiquitination and palmitoylation that are necessary to further develop these projects. I have arranged a group of distinguished mentors, who will provide me with this additional training. During the mentored phase of this award, I will train with Dr. Barth Grant to learn how to approach and solve problems in vesicular trafficking. My mentor, Dr. Kenneth Irvine will provide training in live imaging, and Dr. Marc Gartenberg will provide mentorship on development of the yeast based assay to identify substrates of palmitoyl transferases. The proposed training combined with my previous research experience will enable me to undertake a multipronged comprehensive approach to unravel novel molecular mechanisms regulating Fat signaling. This research plan will also provide insight into pathogenesis of congenital developmental defects arising from disruptions in Fat signaling. The pathway to independence award will enable me to acquire the training and resources I need to achieve my immediate research goals. Further, the proposed training and the innovative research program it supports will help me achieve my short-term goal of obtaining a faculty position at a major university or research institution. The award will further assist me pursue my long-term goal of understanding regulation of organ size and shape during development.